Stacked low profile cooling system and method for making same

ABSTRACT

A stacked array of low profile heat pipes each with a plurality of micro tubes extended therethrough. The stacked low profile heat pipes are placed into thermal connection with heat producing components. A heat transfer fluid is contained in the micro tubes of the low profile heat pipes and removes the heat from the heat producing components.

This application is a Continuation-In-Part of patent application Ser.No. 10/305,662, filed Nov. 26, 2002 now U.S. Pat. No. 6,834,712.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention pertains to a cooling apparatus, and moreparticularly, but not by way of limitation, to a cooling apparatus usingstacked low profile extrusions (LPE's).

2. History of Related Art

As is explained in greater detail hereinbelow, LPE cooling devices areextremely useful in printed circuit board (PCB) level cooling ofelectronic components, and for use as heat exchangers in applicationswhere space is limited and/or low weight is critical.

LPE refers to a heat exchange apparatus comprising an integral piece ofmetal having a series of micro extruded hollow tubes formed therein forcontaining a fluid. LPE's preferably have multi-void micro extrudedtubes designed to operate under the pressures and temperatures requiredby modern environmentally safe refrigeration gases and to resistcorrosion. Aspects of the LPE application to the present invention areset forth and shown in co-pending U.S. patent application Ser. No.09/328,183 assigned to the assignee of the present invention andincorporated herein by reference.

Low profile extrusions can currently be manufactured with a profile, orheight, as low as about 0.05 inches and with tubes of varying innerdiameters. Of course, future advances may allow such low profileextrusions to be manufactured with an even smaller profile. Such lowprofile extrusions have been conventionally used in heat exchangerapplications in the automotive industry, and are commercially availablein strip form (having a generally rectangular geometry) or coil form (acontinuous strip coiled for efficient transport).

An example low profile extrusions is described in a brochure entitled“Thermalex, Inc.—Setting A Higher Standard in Aluminum Extrusions”(hereinafter the “Thermalex Brochure”) provides additional detailregarding the Thermalex low profile extrusions and is incorporatedherein by reference.

U.S. Pat. No. 5,342,189 to Inamura, et al, which is incorporated hereinby reference, provides additional detail regarding an extrusion die formaking such low profile extrusions. The extrusion die is used for makingmulti-cavity flat aluminum tubes, which are used for small heatexchanger components, in automotive air-conditioners, condensers, andradiators. The insert die is composed of a male die section having aprotrusion part and a female die section, having a die cavity, and isheld detachably in a die holder. The male section is a roughlyrectangular plate-shaped component, and has an integrally formed twistprevention region which is inserted into the receiver groove of thefemale section which is integrally formed thereon. The protrusion partdefines the cavity shape of the multi-cavity flat tube, and the femalesection has the die cavity of the required cross sectional shape todefine the outer shape of the tube.

U.S. Pat. No. 5,353,639 to Brookins, et al, which is incorporated hereinby reference, provides additional detail regarding a method andapparatus for sizing a plurality of micro extruded tubes used in suchlow profile extrusions. As described by the Brookins patent, apredetermined number of micro extruded tubes are stacked on the basefence between the fixed side fence and the clamping fence. The internalwebs of the tubes are aligned throughout the stack, perpendicular to theplane of the base fence. The clamping fence is moved toward the stack oftubes to prevent the stack from moving laterally. The die platen ismoved toward the stack of tubes and the mating surface of the die platenis in mating engagement with a side surface of the uppermost tube in thestack. A predetermined amount of pressure is applied to the stack oftubes through the die platen. The pressure is applied equally across theentire side surface of the uppermost tube and is transmitted equallythrough all the tubes of the stack in the sizing die.

Other developments in cooling apparatus may be seen in U.S. Pat. No.5,285,347 to Fox et al., which describes a hybrid cooling system forelectrical components. A hybrid heat sink is specially adapted totransfer heat to two cooling fluids. This heat sink is incorporated intoa cooling system in which some of the electronic components of anelectronic device may be cooled by two cooling fluids and someelectronic components may be cooled by one cooling fluid. The electroniccomponents are mounted on a circuit board. In the Fox reference, one ofthe cooling fluids is air and one is a liquid. The hybrid heat sink isattached to electronic components that cannot be cooled to the normaloperating range by the cooling air alone. The cooling air is caused toflow over the surface of the heat sink, removing some of the heat. Inaddition, the cooling liquid is caused to flow through the heat sink,thereby removing additional heat.

In addition, U.S. Pat. No. 5,901,037 to Hamilton, et al. describes asystem for closed loop liquid cooling for semiconductor RF amplifiermodules. The system comprises a combination of a plurality of elongatedmicrochannels connected between a pair of coolant manifolds forconducting liquid coolant beneath the transistors to dissipate the heatgenerated thereby. The system also includes a heat exchanger, aminiature circulating pump located on the module, and passive checkvalves having tapered passages for controlling the flow of coolant inthe loop. The valve comprises a truncated pyramid-shaped microchannelvalve having no moving parts and is fabricated so as to be a part ofeither the circulating pump assembly, the coolant manifold, or themicrochannels.

SUMMARY OF THE INVENTION

The present invention relates to a low profile extrusion cooling methodand apparatus. More particularly, the present invention relates to astacked low phase plane heat pipe cooling system and method. In oneaspect, the invention includes stacked, low profile phase plane heatpipes, wherein heat transfer fluids contained therein are induced toflow by heat absorbed thereby. The stacked, low profile cooling systemof the present invention includes a first low profile extrusion. Stackedon top of the first phase plane heat pipe is a second low profile phaseplane heat pipe also in thermal contact with first phase plane phaseplane heat pipe. A third low profile phase plane heat pipe may bestacked on top of the first and second low profile phase plane heatpipes. The third low profile phase plane heat pipe is in thermal contactwith top surface of the first low profile phase plane heat pipe.

In another embodiment, a first, second and an optional third thermallyconductive spacer block is provided on the undersurface of each lowprofile phase plane heat pipe and is in thermal contact therewith. Thefirst, second, and optional third thermally conductive spacer blocksprovide a conduit for heat transfer from the heat source up to andthrough the stacked, low profile cooling system.

In yet another embodiment, cooling fins are provided on the undersurfaceand topsurface of the low profile phase plane heat pipes. The coolingfins include elongated arrays in thermal contact with the phase planephase plane heat pipes.

In still another embodiment, the low profile phase plane heat pipes arelow profile phase plane phase plane heat pipes (heat pipes). The lowprofile phase plane phase plane heat pipes are preferably positioned atan angle between 0 and 90 degrees extending laterally from an elementwhich may be either a heat source or the thermally conductive spacerblock. The angle further facilitates the movement of evaporated fluidinto the extremities of the heat pipes for the condensation thereof andthe flow of fluid back into evaporator sections where additional heatmay be absorbed.

The present invention pertains to an improved, high volume, stacked LPEapparatus and method for manufacturing thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the method and apparatus of the presentinvention may be obtained by reference to the following DetailedDescription when taken in conjunction with the accompanying Drawingswherein:

FIG. 1 is a schematic illustration of a low profile extrusion heatexchange apparatus of an unstacked variety, shown as a circulationcooling apparatus for removal of heat from certain heat generatingcomponents;

FIGS. 2 and 3 are schematic illustrations of another embodiment of thelow profile extrusion heat exchange apparatus of an unstacked variety,shown as the heat pipe type cooling apparatus for removal of heat fromcertain heat generating components;

FIG. 4 is a schematic illustration of another embodiment of the lowprofile extrusion heat exchange apparatus of an unstacked variety, shownas heat transfer component of a recirculatory system;

FIG. 5A is a schematic illustration of another embodiment of the lowprofile extrusion heat exchange apparatus of an unstacked variety, shownas a liquid to liquid manifold cooling apparatus;

FIG. 5B is a schematic illustration of another embodiment of the lowprofile extrusion heat exchange apparatus of an unstacked variety, shownas a liquid to air manifold cooling apparatus;

FIG. 5C is a schematic illustration of another embodiment of the lowprofile extrusion heat exchange apparatus of an unstacked variety, shownas an air to air manifold cooling apparatus;

FIG. 6 is a is a schematic illustration of a method and apparatus formanufacturing heat pipes according to an embodiment of the heat exchangeapparatus of an unstacked variety;

FIG. 7 is a schematic illustration of another embodiment of the lowprofile extrusion heat exchange apparatus of an unstacked variety, shownas heat pipe base/fin cooling apparatus;

FIG. 8 is a schematic illustration of another embodiment of the lowprofile extrusion heat exchange apparatus of an unstacked variety, shownas a base/heat pipe fin cooling apparatus;

FIG. 9 is an illustration of one aspect of a stacked low profile coolingsystem constructed in accordance with the principles of the presentinvention;

FIG. 10 is a perspective view of an embodiment of the stacked, lowprofile cooling system of the present invention;

FIG. 11 is a side view of an embodiment of the stacked, low profilecooling system of the present invention;

FIG. 12 is an embodiment of a cooling system illustrating variousaspects of the operation thereof in accordance with the principles ofthe present invention;

FIG. 13 is an illustration of a laptop computer including an embodimentof the present invention; and

FIG. 14 is an illustration of a laptop computer including an alternateembodiment of the present invention.

FIG. 15 is a side elevational view of the present invention illustratinga stacked cooling system bonded together at one end for facilitatinggreater heat removal.

FIG. 16 is an enlarged view of FIG. 15 illustrating the stacked coolingsystem of the present invention.

DETAILED DESCRIPTION

The preferred embodiments of the present invention and their advantagesare best understood by referring to FIGS. 1–8 of the drawings, likenumerals being used for like and corresponding parts of the variousdrawings. The present invention is illustrated herein by example, andvarious modifications may be made by a person of ordinary skill in theart.

FIG. 1 is a schematic illustration of a first preferred embodiment ofthe present invention showing a cooling apparatus 10 used for removingheat from certain heat generating components 12 mounted on a printedcircuit board 14. The printed circuit board 14 may be housed in a hostelectronic device (not shown) such as computer, a laptop or notebookcomputer, or other electronic equipment. Due to the ongoingminiaturization of such host electronic devices, the heat generatingcomponents 12 are often located in an area of the printed circuit board14 and of the host electronic device where space is extremely limited,especially in the “z”, or height dimension.

The cooling apparatus 10 generally includes a conventional liquid-to-airheat exchanger 16, an inlet tube 18, a low profile extrusion 20, anoutlet tube 22, a conventional pump 24, and tubing 26. The low profileextrusion 20 has a plurality of micro tubes 21, each micro tube 21having a micro tube inlet 21 a and a micro tube outlet 21 b.

Micro tubes 21 are formed by a plurality of longitudinal members. Thelongitudinal members may be vertical or may be offset from vertical. Apreferred offset from vertical is between about 5° and 60°. Morepreferably, longitudinal members are offset from vertical by 30°.Furthermore, longitudinal members may be provided with a capillarygroove. The capillary groove may be positioned on an external surface oron the longitudinal members. Further, the capillary grooves may beprovided in groups of one, two, three or more.

Referring again to FIG. 1, the extrusion 20 is preferably formed with aflat surface on its underside 20 a for contacting heat generatingcomponents 12, and may be formed with external fins on its top side 20 bto maximize heat transfer, if space allows. It is notable that the microtubes 21 formed in the extrusion 20 may be of nearly any geometry andthat shapes with flattened heat transfer surfaces are generallypreferred, but tubes of any shape could be used with varying degrees ofefficiency. This is best illustrated in FIGS. 7 and 8, where flatextrusions 20 with rectangular micro tubes 21 are shown. Extrusion 20 isalso preferably formed with at least one solid channel (not shown) formounting to printed circuit board 14. Conventional thermal interfacematerial (not shown) is preferably provided between low profileextrusion 20 and heat generating components 12.

The micro tube inlets 21 a of the micro tubes 21 in the extrusion 20 areinterconnected in fluid communication, and to the inlet tube 18, by aninlet end cap 28 a. Similarly, the micro tube outlets 21 b of the microtubes 21 in the extrusion 20 are interconnected in fluid communication,and to the outlet tube 22, by an outlet end cap 28 b. Alternatively,micro tube outlets 21 a and/or 21 may be sealed by crimping the lowprofile member 20. Micro tubes outlets 21 a and/or 21 b may beindividually sealed or connected in fluid communication. The heatexchanger 16 may contain a fluid reservoir (not shown) therein forhousing a fluid such as water, glycol, alcohol, or other conventionalrefrigerants. In addition, a wick, such as screen may be provided withinone or all of micro tubes 21. In this case, fluid from the heatexchanger 16 is circulated through the inlet tube 18, the low profileextrusion 20, the outlet tube 22, and the tubing 26 via the pump 24.Alternatively, the entire cooling apparatus 10 may be evacuated andcharged with fluid which is then circulated via the pump 24.

During operation of the host electronic device, heat generated by heatgenerating components 12 is transferred from heat generating components12 to an evaporator section of low profile extrusion 20, to the fluidcirculating within low profile extrusion 20, and then to heat exchanger16 from a condenser section of low profile extrusion 20. Heat exchanger16 removes the heat from the fluid in a conventional manner. Preferably,an airflow 30 is passed over heat exchanger 16 to aid in such heatremoval. Cooling apparatus 10 thus efficiently removes heat from alimited space, low profile area within the host electronic device (thelocation of low profile extrusion 20) to an area where it can be removedat a more convenient location and envelope (the location of heatexchanger 16).

FIGS. 2 and 3 are schematic illustrations of a second preferredembodiment of the present invention showing a cooling apparatus 40 usedfor removing heat from heat generating components 12 on printed circuitboard 14. Referring first to FIG. 2, cooling apparatus 40 generallycomprises a low profile extrusion 42 manufactured as a heat pipe capableof phase change heat transfer. A preferred method of making a lowprofile heat pipe extrusion 42 is described in greater detailhereinbelow. The low profile heat pipe extrusion 42 is preferably formedwith micro tubes 41, each micro tube 41 having a conventional wickstructure such as internal fins, grooved inner sidewalls, or metalscreens, so as to maximize their heat transfer capability via capillaryaction.

To form a heat pipe, the micro tubes 41 of the low profile heat pipeextrusion 42 are evacuated and then charged with a fluid such as water,glycol, alcohol, or other conventional refrigerants before sealing theends 41 a and 41 b of the micro tubes 41. The ends may be sealed bycrimping. By providing vertically offset longitudinal members,longitudinal members tend to lay over during crimping rather thanbuckling. Therefore, vertically offset members may be advantageous. Asis known in the art, a heat pipe generally has an effective thermalconductivity of several multiples higher than that of a solid rod. Thisincrease in efficiency is due to the fact that the phase change heattransfer coefficients are high compared to the thermal conductivity ofconventional materials.

The low profile heat pipe extrusion 42 is preferably formed into anevaporator section or first portion 44 for contacting heat generatingcomponents 12 and a raised or condenser section second portion 46. Firstportion 44 and second portion 46 are preferably substantially similar inconstruction to low profile extrusion 20 of FIG. 1, except end caps 28are not required. First portion 44 acts as the evaporator section of theheat pipe, and second portion 46 acts as the condenser section of theheat pipe.

During operation of the host electronic device, heat generated by heatgenerating components 12 is transferred from heat generating components12 to first portion 44. This heat causes the liquid within the microtubes 41 in first portion 44 to change to vapor, consuming some of thegenerated heat. Because the vapor is less dense than the surroundingliquid, the vapor and associated heat rise into the micro tubes 41 insecond portion 46. Of course, heated liquid may also be transferred fromfirst portion 44 to second portion 46 via the capillary action of thewick structures of the micro extruded tubes therein. In second portion46, the vapor condenses into liquid onto the inner side walls of themicro extruded tubes 41. The heat generated by the condensationreaction, as well as any heat transferred via capillary action of thewick structure, is then transferred to air flow 48. Cooling apparatus 40thus efficiently removes heat from a limited space, low profile areawithin the host electronic device (the location of first portion 44) toan area where it can be removed at a more convenient location andenvelope (the location of second portion 46). Of course, if low profileheat pipe extrusion 42 is formed with internal wick structures, it isnot necessary that second portion 44 be raised from, or higher than,first portion 42.

Referring now to FIG. 3, low profile heat pipe extrusion 42 is shown inoperation with a conventional thermoelectric cooler (TEC) 50 in contactwith one of heat generating components 12. A preferred TEC is sold byMarlow Industries, Inc. of Dallas, Tex. TEC 50 facilitates the heattransfer between the heat generating component 12 and first portion 44of low profile heat pipe extrusion 42, and thus is preferred for usewith heat generating components 12 that have high power densities.

FIG. 4 is a schematic illustration of a third preferred embodiment ofthe present invention showing a cooling apparatus 60 used for removingheat from a fluid 62, such as water, glycol, alcohol, or otherconventional refrigerants. Fluid 62 is then used to cool conventionalheat generating components, such as heat generating components 12 ofprinted circuit board 14. By way of example, cooling apparatus 60 may beused in place of conventional heat exchanger 16 in FIG. 1.

Cooling apparatus 60 generally comprises a low profile extrusion 64, aninlet end cap 63 a, an inlet tube 66, an outlet end cap (not shown), anoutlet tube (not shown), thermoelectric coolers 52, and conventionalbonded fin heat sinks 68 and 70. The low profile extrusion 64 ispreferably substantially similar in construction to low profileextrusion 20 of FIG. 1, with a plurality of micro tubes (not shown)having a micro tube inlet and a micro tube outlet (not shown). The microtube inlets of the micro tubes in the extrusion 64 are interconnected influid communication, and to the inlet tube 66, by the inlet end cap 63a. Similarly, the micro tube outlets of the micro tubes in the extrusion64 are interconnected in fluid communication, and to the outlet tube, byan outlet end cap.

The low profile extrusion 64 preferably has generally flat bottom andtop surfaces for contact with thermoelectric coolers (TEC) 52. Theconventional bonded fin heat sink 68 is coupled to TECs 52 on the topsurface of low profile extrusion 64, and the conventional bonded finheat sink 70 is coupled to TECs 52 on the bottom surface of low profileextrusion 64.

In operation, the low profile extrusion 64 serves as a manifold, and theTECs 52 remove heat from fluid 62 flowing through the micro tubes of thelow profile extrusion 64. This removed heat is transferred from TECs 52to bonded fin heat sinks 68 and 70, which dissipate the heat toatmosphere in a conventional manner. Preferably, airflows 72 and 74 passover and through heat sinks 68 and 70 to facilitate such heatdissipation.

Low profile extrusion 64 has a smaller size and mass than conventionalheat exchanger manifolds. For example, a conventional manifold has aminimum profile, or height, in the “z” direction of about 0.75 inches,and low profile extrusion 64 may have a profile as low as about 0.1inches. The reduced mass of low profile extrusion 64 is believed toproduce a cooling apparatus 60 with a near zero time constant,increasing startup performance and temperature control. Therefore,cooling apparatus 60 is especially advantageous in applicationsinvolving lasers. The wavelength of a laser beam, and thus beamproperties, is strongly influenced by temperature, and the tightertemperature control believed to be provided by cooling apparatus 60 isextremely beneficial.

FIGS. 5A, 5B, and 5C are schematic illustrations of fourth, fifth, andsixth preferred embodiments of present invention. FIG. 5A shows acooling apparatus 80 having a plurality of low profile extrusions 64 andTECs 52 arranged in a serial fashion. A TEC 52 is disposed between, andis in contact with, each of the extrusions 64. Only one low profileextrusion 64 and one TEC 52 is numbered in FIG. 5A for clarity ofillustration. Fluid 62 enters each extrusion 64 via inlet 66 and exitseach extrusion 64 via an outlet 82. In operation, TECs 52 remove heatfrom fluid 62 flowing through low profile extrusions 64. This removedheat is transferred to airflow 84 passing over cooling apparatus 80.

FIG. 5B shows a cooling apparatus 90 having a plurality of low profileextrusions 64, TECs 52, and low profile heat pipe extrusions 92 arrangedin a serial fashion. More specifically, a TEC 52 is disposed between,and is in contact with, each low profile extrusion 64 and low profileheat pipe extrusion 92. Only one low profile extrusion 64, one TEC 52,and one low profile heat pipe extrusion 92 are numbered in FIG. 5B forclarity of illustration. Each low profile heat pipe extrusion 92 ispreferably substantially similar in construction to low profile heatpipe extrusion 42 ∘ FIG. 1, excluding raised portion 46. Fluid 62 enterseach extrusion 64 via inlet 66 and exits each extrusion 64 via outlet82. In operation, each TEC 52 removes heat from fluid 62 flowing throughan adjacent low profile extrusion 64. This removed heat is transferredto the evaporator portion 92 a of the adjacent low profile heat pipeextrusion 92. The heat is then transferred to the condenser portion 92 bof the low profile heat pipe extrusion 92, as is explained hereinabovein connection with low profile heat pipe extrusion 42 of FIGS. 2 and 3.An airflow 84 passing over cooling apparatus 90 dissipates heat fromeach condenser portion 92 b of each low profile heat pipe extrusion 92.

FIG. 5C shows a cooling apparatus 100 having a plurality of TECs 52 andlow profile heat pipe extrusions 92 arranged in a serial fashion. Morespecifically, a TEC 52 is disposed between, and is in contact with, eachlow profile heat pipe extrusion 92, and the “free end” of adjacent lowprofile heat pipe extrusions 92 extend in opposite directions. Only oneTEC 52 and two low profile heat pipe extrusions, 92′ and 92″, arenumbered in FIG. 5C for clarity of illustration. In operation, a hotairflow 102 flows over each evaporator portion 92 a of low profile heatpipe extrusions 92′. This heat is transferred from evaporator portion 92a to condenser portion 92 b of extrusion 92′, as is explainedhereinabove in connection with low profile heat pipe extrusion 42 ofFIGS. 2 and 3. Condenser portion 92 b of extrusion 92′ is in contactwith TEC 52. The TEC 52 removes heat from condenser portion 92 b ofextrusion 92′ and transfers it to evaporator portion 92 a of low profileheat pipe extrusion 92″. This heat is then transferred from evaporatorportion 92 a to condenser portion 92 b of extrusion 92″. Cold airflow104 passing over condenser portions 92 b of each extrusion 92″dissipates heat from cooling apparatus 100.

Cooling apparatus 80, 90, and 100 have the same applications andadvantages of cooling apparatus 60 described hereinabove. As will beappreciated by one skilled in the art, cooling apparatus 60, 80, and 90may also be operated as heating apparatus by using thermoelectriccoolers (TECs) 52 to heat, rather than to cool, a fluid.

FIG. 6 is a schematic illustration of a method and apparatus formanufacturing heat pipes according to a seventh preferred embodiment ofthe present invention. As noted hereinabove, the preferred apparatus andmethod may be utilized to make low profile heat pipe extrusions 42 and92 of FIGS. 2, 3, 5B, and 5C. However, the preferred apparatus andmethod may also be utilized to make extruded hollow tubes for other heatexchangers and heat pipes.

Apparatus 110 generally includes an oven 112 having an insulatedhousing. A vacuum station 114 and a fluid charging station 116 are influid communication with oven 112. Alternatively, stations 114 and 116may be separate from oven 112. A coil 118 is disposed within a portionof oven 112 on a conventional automatic feed system. Coil 118 may be acoil of hollow tubing, a coil of low profile extrusion, or a coil ofother conventional extrusion having a series of extruded hollow tubestherein. Furthermore, coil 118 comprises any material that can be formedand welded with any fluid fill. This includes, but is not limited toaluminum, stainless steel, carbon steel, copper, and titanium alloys. Anultrasonic welder/sealer is also provided. One model of ultrasonicwelder/sealer is the Ultraseal® series sold by American Technology, Inc.of Shelton, Conn. A brochure entitled “Ultraseal®-20 20 kHz PortableUltrasonic Metal Tube Sealer” (hereinafter the “Amtech Brochure”)provides additional information regarding the Ultraseal® series ofultrasonic welder/sealers and is incorporated herein by reference. Apreferred ultrasonic welder/sealer is the Stapla Ultrasonic gantry styleseam welder.

In a conventional process, the first step is actually forming andcutting the heat exchanger, heat pipe, or extruded tubes into thedesired configuration. Next, this preformed system is evacuated andcharged with a fluid such as water, glycol, alcohol, or otherconventional refrigerants. The system is then sealed, completing theprocess. Conventional processes are expensive because they are laborintensive and require long setup times for different configurations ofheat exchangers, heat pipes, or extruded tubes.

However, apparatus 110 may be used to efficiently and economicallyproduce heat exchangers, heat pipes, and extruded tubes, including lowprofile extrusions, according to the following preferred process. First,coil 118 is placed within a heat producing device such as oven 112 onthe automatic feed system. Second, coil 118 is evacuated using vacuumstation 114. Preferably, coil 118 is pulled down to a vacuum of about10⁻⁷ torr for a period lasting approximately twenty four hours to manyweeks depending on performance requirements. Third, coil 118 is chargedwith a known amount of fluid, such as water, glycol, alcohol, acetone orother conventional refrigerants, using charging station 116. Acetone isthe preferred fluid. Alternatively, coil 118 may be evacuated andcharged outside oven 112. Fourth, oven 112 heats coil 118 until at leastsome of the fluid is in the vapor phase, and the vapor fills theinterior of coil 118 evenly. Fifth, using the automatic feed system, theheated and charged coil 118 is reeled out. Preferably the fluid exitsthe oven 112 at approximately 40° C. to 60° C. allowing enough thermalinertia to draw vapor into the extrusion external to the oven. Atemperature sender container may be provided to ensure that the fluidexit temperature is maintained at a desired level. The coil is thenprocessed by crimping, sealing, and cutting the coil 118 into desiredlengths. The temperature difference between the oven 118 and the ambientair (or air-conditioned air) temperature condenses the charging fluid ineach pipe before it is crimped. These temperatures and flows are used tocontrol the individual heat pipe fills via a weight analysis. A computerand scale monitor the weight of each part and adjust the oventemperatures accordingly. Subsequent steps comprise crimping, sealingand cutting the coil 118. A hydraulic press, pneumatic or mechanicalmeans may be used for crimping. An ultrasonic welder/sealer, or anotherstandard welding method such as laser electron beam, resistive, TIG, orMIG welding may be used during the sealing stage. Ultrasonic welding isthe preferred process. A plasma cutter, or other standard welding methodmentioned herein may be used in the cutting stage. However, the plasmacutter is the preferred method. Finished product is collected withincontainer 122. In this manner, heat exchangers, heat pipes, and extrudedtubes, including low profile extrusions, are formed while charged withfluid, significantly reducing the setup time and vacuum expense overconventional processes.

In addition, by separating the coil side of the process from thecrimping, sealing and welding process steps, the temperatures for theprocess steps can be adjusted so as to be in the fluid range for theworking fluid. Thus, if a cryogenic heat pipe (charging fluid istypically a gas at normal room temperature) is to be manufactured, thetemperature of the process steps would be adjusted such that thecharging fluid is a liquid. In a similar manner, high temperature heatpipes, where the charging fluid is typically a solid at roomtemperatures, can be manufactured.

Referring now to FIG. 7, there is shown an illustration of anotherembodiment of a low profile cooling system of an unstacked variety. Acooling apparatus 210 is used for removing heat from heat generatingcomponents 12 on a printed circuit board 14. The cooling apparatus 210comprises a low profile extrusion 220 manufactured as a heat pipecapable of phase change heat transfer. The low profile heat pipeextrusion 220 is formed having a plurality of micro tubes 223,preferably having therein a conventional wick structure such as internalfins, grooved inner side walls, or metal screens, so as to maximize theheat transfer capability via capillary action. The micro tubes 223 ofthe low profile heat pipe extrusion 220 are evacuated and then chargedwith a fluid such as water, glycol, alcohol, or other conventionalrefrigerants, before the ends of the micro tubes are sealed.

Referring still to FIG. 7, the low profile heat pipe extrusion 220 has afirst surface 221 for engaging the heat generating components 12 andreceiving heat therefrom. On a second surface 222 of the low profileextrusion 220, a conventional bonded fin heat sink 230 or a plurality ofcooling fins are mounted to the low profile extrusion 220. Preferably,the micro tubes 223 are disposed in a direction perpendicular to thefins 230 for transferring heat between each of the individual fins 230.The heat transfer between the individual fins 230 promotes an evendistribution of heat across each of the fins 230. However, the microtubes 223 can be oriented for the transfer of heat along the length ofthe fins 230. Additionally, in one embodiment, the micro tubes 223 ofthe low profile extrusion 220 are oriented for disbursing heat from theheat generating components 12 to areas of the low profile extrusion 220which are not in contact with the heat generating components 12.

Still referring to FIG. 7, the use of the low profile extrusion 220 fortransferring heat in the cooling apparatus 210 increases the effectivesurface area that is transferring heat from the heat generatingcomponents to the cooling fins 230. The resulting cooling apparatus istherefore smaller in size and lighter in weight for the same effectivecooling attributes. In some embodiments, the low profile cooling systemof an unstacked variety can decrease the weight of an apparatus forcooling a heat generating component by as much as 50% over traditionalfins mounted via a metal plate.

Referring now to FIG. 8, there is shown an illustration of anotherembodiment of a low profile cooling system of an unstacked variety,showing a cooling apparatus 250 used for removing heat from heatgenerating components 12 on printed circuit board 14. The coolingapparatus generally comprises a base 260 and a plurality of low profileextrusion fins 270. The base 260 has a first side 261 for transferringheat between the cooling apparatus 250 and heat generating components12. The base 260 also has a second surface 262 for mounting the lowprofile extrusion fins 270.

Referring still to FIG. 8, the low profile extrusion fins 270 are lowprofile extrusions manufactured as a heat pipe capable of phase changeheat transfer. The low profile extrusion fins 270 are preferably formedwith a plurality of micro tubes 273, each internally having aconventional wick structure such as fins, grooved side walls, or metalscreens, so as to maximize the heat transfer capability via capillaryaction. The micro tubes 273 of the low profile extrusion heat piping 270are evacuated and then charged with a fluid such as water, glycol,alcohol, or other conventional refrigerants, before the micro tubes 273are sealed.

Still referring to FIG. 8, a first end 271 of the low profile extrusionfins 270 is mounted to the second surface 262 of the base 260 with asecond end 272 extending outwardly therefrom. The plurality of lowprofile extrusion fins 270 are preferably mounted in rows for convectionheat transfer to the surrounding environment. In one embodiment, thebase 260 can also be formed from a low profile extrusion similar to thelow profile extrusion 220 in FIG. 7.

Referring still to FIG. 8, the use of the heat pipe type low profileextrusion fins 270 in the cooling apparatus 250 increases the effectivesurface area in which heat is transferred from the heat generatingcomponents to the surrounding environment via the base 260. Theresulting cooling apparatus is therefore smaller in size and lighter inweight for the same effective cooling attributes.

Referring now to FIG. 9, there is shown an illustration of a stacked,low profile cooling system 400 of the present invention, with an arrayof cooling fins secured to an assembly of the low profile extrusion heatpipes described above. More specifically, the stacked, low profilecooling system 400 includes a first phase plane heat pipe 401 with fins403 secured to an undersurface thereof, and fins 405 secured to a topsurface thereof. Stacked on top of the phase plane heat pipe 401 is asecond phase plane heat pipe 410, also in thermal contact with thecooling fins 405 disposed on the underside thereof, and further having aset of cooling fins 412 disposed on a top surface thereof. A firstthermally conductive spacer block 422 is disposed between the firstphase plane heat pipe 401 and the second phase plane heat pipe 410. Athird phase plane heat pipe 415 is stacked on top of the first andsecond phase plane heat pipes 401 and 410 also in thermal contact withthe cooling fins 412 and further being assembled with cooling fins 417stacked on a top surface thereof. Similarly, a second thermallyconductive spacer block 424 is disposed between the second phase planeheat pipe 410 and the third phase plane heat pipe 415. It may be seenthat the cooling fins 403, 405, 412, and 417 include elongated arrays inthermal contact with said phase plane heat pipes. As shown herein, anangle between 0 and 90 degrees is suggested relative to the angulatedportion of the phase plane heat pipe extending laterally outwardly fromelement 426, which may be a heat source or a third thermally conductivespacer block disposed beneath the first phase plane heat pipe 401 with aheat generating component 420 disposed therebeneath (as shown in FIG.9). The heat source 420 may be any of a plurality of heat generatingcomponents, such as computer chips and/or elements within an electricalcircuit. As also referenced in FIG. 9, the type of material, eithercopper or aluminum, has been specified on the thermally conductivespacer blocks 422, 424, and 426. The thermally conductive spacer blocks422, 424, and 426 provide a conduit for heat transfer from the heatgenerating component 420 up to and through the stacked, low profilecooling system of the present invention.

Referring now to FIG. 10, there is shown a perspective view of thestacked, low profile cooling system 400 of FIG. 9. In this particularembodiment, air flow is in the direction of arrow 430. Air is permittedto flow around and through the fins 417, 412, 405, and 403 to providethe cooling of the surfaces of the phase plane heat pipes 401, 410, and415 in accordance with the principles of the present invention. In thisway the stacked, low profile cooling system 400 provides improvedoperational efficiencies.

Referring now to FIG. 11, there is shown a side view of the stacked, lowprofile cooling system 400 constructed in accordance with the principlesof the present invention. The stacked, low profile cooling system 400,as described above, includes a condenser section 440 where condensingoccurs. Likewise, an evaporator section 444 is illustrated in agenerally centrally disposed area of the stacked, low profile coolingsystem 400 wherein heat is absorbed from the heat source 420. Theabsorption of the heat by the stacked, low profile cooling system 400 ofthe present invention causes evaporation and the movement of the fluidwithin the phase plane heat pipes 401, 410, and 415 through adiabaticsections 446 wherein the fluid is allowed to expand without either lossor gain of heat, as is the technical definition of adiabatic. The angleof 0 to 90 degrees as shown herein further facilitates the movement ofthe evaporated fluid into the extremities of the heat pipes for thecondensation thereof in the condenser sections 440, and the flow offluid back through the adiabatic sections 446 and into the evaporatorsection 444 where additional heat may be absorbed.

Referring now to FIGS. 9, 10, and 11, the stacked, low profile coolingsystem 400 of the present invention illustrates phase plane heat pipesin an innovative manner providing a low profile and lightweight coolingalternative to conventional heat sinks. The low profile and flat phaseplane heat pipes provide an ideal surface to attach to a heat generatingcomponent and fins to cool the component. Through the stacking of phaseplanes, heat removal rates of over 100 watts can be achieved for astandard 31×31 mm microprocessor, or keep lower wattage microprocessorsat a lower operating temperature.

Referring still to FIGS. 9, 10 and 11 in combination, there is shown thestacks of the phase plane heat pipes 401, 410, and 415 that provide alow profile, high watt density heat removal design. The materials ofconstruction preferably include copper, aluminum, or other thermallyconductive substances. This is particularly true of the thermallyconductive spacer blocks 422, 424, and 426 above described and securedto the heat generating component 420 (as shown in FIG. 9). Theattachment process can be done through mechanically compressing the heatgenerating device to the heat sink with a thermal pad or thermal greasetherebetween. The specific mounting mechanism is not shown herein andcan include a variety of methods currently used in the heat sink marketplace. The base stack that is in contact with the heat generatingcomponent may also be the phase plane heat pipe as well. The fins 403,405, 412, and 417 can be attached on both sides of the phase plane heatpipes 401, 410, and 415 providing surface area for the air/heat exchangeto reduce the temperature of the cooling system 400 of FIGS. 9–11, andthus the heat generating component 420. Air is ducted across the coolingfins 403, 405, 412, and 417 and the heat pipes 401, 410, and 415 in themanner shown in FIGS. 9–11.

Again referring to the operation of the stacked, low profile coolingsystem 400 of the present invention, the evaporator section 444 comprisethat region of the phase plane heat pipes where the heat generatingcomponent 420 is positioned, as best illustrated in FIG. 11. Thecondenser sections 440 of the phase plane heat pipes located toward theends thereof provide for the recirculation of the fluid therein andthrough the adioabatic sections 446. Significant increases inperformance are provided when gravity aids the operation of theindividual phase plane heat pipes. The design can have an angular rangefrom 0 degrees (horizontal) to 90 degrees (vertical), depending on thedesign parameters required for a particular device. Through the stackingapproach and increased effective fin-surface area, the stacked, lowprofile cooling system of the present invention will provide superiorperformance in a low profile package.

Referring now to FIG. 12, there is shown an alternative embodiment ofthe stacked, low profile cooling system of the present inventionincorporating a possible design for a laptop computer. A heat generatingcomponent 487 is shown in phantom and may comprise a printed circuitboard disposed in a laptop computer. In this particular embodiment, airis sucked into a fan 480 as shown by arrow 486. As shown by arrow 485,air is blown out the sides through fin stock 482 mounted upon at leastone phase plane heat pipe 484 of the type set forth and described inFIGS. 9–11. The evaporator section 470 of the phase plane heat pipe 484is thermally and mechanically affixed to the heat generating component487. The fins 482 are placed on the condenser section 471 to aid in thecooling thereof. A 0 degrees to 90 degrees orientation may be placed onthe phase plane 484 between the evaporator section 470 and the condensersection 471. In another embodiment, a stacked array of heat pipes may beutilized in accordance with the stacked, low profile cooling system ofthe present invention, as well as the utilization of a phase plane heatpipe on both sides of the fan 480.

Referring now to FIG. 13, a laptop computer 500 including an embodimentof the present invention, as shown in FIG. 12, is described. The fan 480is disposed in a corner beneath a keyboard 502 and above a heat source501 such as a circuit board. Air is drawn in to the fan 480 anddispersed outward through the fin stock 482. Although the fin stock 482is illustrated as being positioned vertically in the laptop, the finstock 482 may also be positioned in other orientations, such ashorizontally.

Referring now to FIG. 14, there is shown an alternate embodiment of thepresent invention disposed in a laptop computer 500. In this embodiment,a fan 550 is connected with two fin stocks 560 for dispersing heat. Thefan 550 may be located anywhere within the laptop 500 and have one ormore fin stocks 560 associated with the fan 550. The fin stocks 560 maybe located at opposite sides of the fan 550, or form an L-shape. The fan550 may also have more than two fin stocks 560 associated therewith.

Various embodiments of the stacked, low profile cooling system of thepresent invention may also include cross configurations where the phaseplane heat pipes extend orthogonally one to the other and/or at anglesacute to each other for purposes of positioning around components withinan electrical system, such as a computer, and/or to improve air flowthereacross to improve the thermal efficiency thereof.

Referring now to FIG. 15, there is shown a side elevational view of anembodiment of the present invention. In this particular embodiment,there is shown a stacked, low profile cooling system 600 similar to thecooling systems above described in relation to FIGS. 9–14. Specifically,a first phase plane 602 is provided with a fin stock 604 in thermalcontact with a portion of the outer surface thereof. A second phaseplane 606 is provided in thermal contact with fin stock 604 and thefirst phase plane 602. The second phase plane 606 further has a finstock 608 in thermal contact with a portion of the outer surfacethereof. Stacked on top of phase plane heat pipes 602 and 606 is a thirdphase plane heat pipe 610, also in thermal contact with fin stock 608,and having a fin stock 612 in thermal contact with a portion of theouter surface thereof. Block 614 may be in thermal contact with a heatgenerating component (not shown). At an end opposite block 614, phaseplane heat pipes 602, 606, and 610 are coupled together at region 616.Region 616 further has fin stock 618 in thermal connection therewith.Although three phase plane heat pipes are illustrated in FIG. 15, anynumber of phase plane heat pipes may be used depending on theapplication.

Referring still to FIG. 15 phase plane heat pipes 602, 606, and 610 arecoupled (or bonded) at one end with a thermally conductive block 614.The cooling system 600 is similar in operation to the phase plane heatpipes aforementioned with reference to FIGS. 3,4 and 9–14. Specifically,heat generated by a heat generating element causes cooling fluidcontained in internal micro tubes of the phase plane heat pipes toevaporate in the evaporator section 620. The absorption of the heat bythe stacked, low profile cooling system 600 of the present inventioncauses evaporation and the movement of the fluid within the phase planeheat pipes 602, 606, and 612 through adiabatic sections 622 wherein thefluid is allowed to expand without either loss or gain of heat, as isthe technical definition of adiabatic. The cooling system 600 may beplaced at an angle of 0 to 90 degrees in relation to the heat generatingelement (not shown) to further facilitate the movement of the evaporatedfluid into the extremities of the heat pipes for the condensationthereof in the condenser sections 624, and the flow of fluid backthrough the adiabatic sections 522 and into the evaporator section 520where additional heat may be absorbed.

Referring now to FIG. 16, There is shown an enlarged view of coolingsystem 600, with phase plane heat pipes 602, 606, and 610 bondedtogether and in thermal contact with heat generating component 700. Asused in this manner, cooling system 600 provides multiple advantagesover prior art devices for removing heat from the heat generatingelement 700. First, with the addition of fins in the condenser region, agreater amount of heat may be removed from the heat generating element700. Second, with the addition of the block 614 (FIGS. 15 and 16), thepresent invention may be mounted to heat generating element 700 androtated for maximum efficiency though gravity assistance in theadiabatic process. The present invention provides 360 degrees of freedomon which to place the device. It does not have to be placed horizontallyin relation to the heat generating element 700.

In operation, the present invention is useful in applications, such asnotebook computers, computer network servers, desktop computers, powersupplies, chillers/heaters, and telecommunication applications.

The present invention is particularly well suited for applicationsrequiring a heat removal apparatus that has minimal spacial area, suchas notebook computer applications. A heat pipe according to theprinciples of the present invention may be extruded with various twistsand turns to maximize heat removal ability in a minimal amount of space.

For applications involving high performance microprocessors, a heat pipewith fins attached opposite one another on the top and bottom surfacesof heat pipe may be used. This configuration allows improved heatremoval characteristics.

Further, The cooling system 600 of the present invention is advantageousin many areas, including RF amplifiers and seat coolers for automobiles.Further, the number of phase planes and location thereof may change perapplication.

It is believed that the operation and construction of the presentinvention will be apparent from the foregoing description of a preferredembodiment. While the device shown is described as being preferred, itwill be obvious to a person of ordinary skill in the art that variouschanges and modifications may be made therein without departing from thespirit and scope of the invention as defined in the following claims.Therefore, the spirit and the scope of the appended claims should not belimited to the description of the preferred embodiments containedherein.

1. A cooling system for removing heat from at least one heat generatingcomponent, said cooling system comprising: a plurality of low profilephase plane heat pipes having first and second end sections and disposedin thermal contact one with the other, said low profile phase plane heatpipes having a plurality of micro tubes disposed therein and having atleast one fin stock disposed outwardly along a portion thereof; a heattransfer fluid contained within said plurality of micro tubes; acoupling element adapted for coupling said plurality of low profilephase plane heat pipes at said first end section thereof, said couplingelement having a surface adapted for thermal contact with the heatgenerating component for removing heat therefrom; and said phase planeheat pipes diverging outwardly one from the other beyond said first endsection, and forming said second end section in increased spacedrelationship relative to said first end section for accommodating saidat least one fin stock in thermal contact along a portion thereof forfacilitating enhanced thermal transfer therefrom.
 2. A method ofremoving heat from at least one heat generating component, comprisingthe steps of: providing a plurality of phase plane heat pipes havingfirst and second end sections and each having a plurality of micro tubesdisposed internally thereof and containing a heat transfer fluidtherein; coupling said plurality of heat pipes in thermal contact onewith the other along said first end sections thereof with a couplingelement to improve the thermal efficiency thereof; diverging at leastone of said plurality of phase plane heat pipes outwardly from anotherbeyond said first end sections of said plurality of phase plane heatpipes; mounting at least one fin stock along said outwardly divergedsecond end sections of said heat pipes for dissipating heat therefrom;and securing said coupling element adjacent to said heat generatingcomponent.
 3. A cooling system for removing heat from at least one heatgenerating component, said cooling system comprising: a plurality ofphase plane heat pipes; a heat transfer fluid disposed within said heatpipes; an evaporator section formed along a first end portion of saidheat pipes for allowing said fluid to heat and evaporate therein; acondenser section formed along a second end portion of said heat pipesfor dissipating heat from said fluid and allowing the evaporated fluidto condense; at least one fin stock secured outwardly of said heat pipesalong at least a portion of said condenser section; an adiabatic sectionof said heat pipes disposed between, and adapted for, transferring saidfluid between said evaporator section and said condenser section; acoupling element adapted for coupling said plurality of phase plane heatpipes in thermal contact one with the other to improve the thermalefficiency thereof; and wherein at least one of said plurality of phaseplane heat pipes diverges outwardly from at least one of said evaporatorsection and said adiabatic section for increasing the distance betweensaid heat pipes along said condenser section and contiguous with saidfin stock secured therealong.
 4. The cooling system of claim 3, whereinsaid plurality of phase plane heat pipes are disposed in generallyparallel-spaced relationship along said condenser section.
 5. Thecooling system of claim 3, wherein said plurality of phase plane heatpipes are disposed in generally parallel spaced relationship along saidevaporator section.
 6. The cooling system of claim 3, wherein theplurality of phase plane heat pipes are spaced substantially parallel toone another within at least a portion of the adiabatic section.
 7. Thecooling system of claim 3, wherein the plurality of phase plane heatpipes comprises three phase plane heat pipes.
 8. The cooling system ofclaim 3, wherein at least one of the plurality of phase plane heat pipesis in thermal contact with the at least one fin stock for furtherfacilitating condensation of the fluid.
 9. The cooling system of claim3, wherein a central one of the plurality of phase plane heat pipes isin thermal contact with fin stock on two outer surfaces of said centralphase plane heat pipe.
 10. The cooling system of claim 3, wherein anouter one of the plurality of phase plane heat pipes is in thermalcontact with fin stock on one outer surface of said outer phase planeheat pipe.
 11. The cooling system of claim 3, wherein at least one ofthe plurality of phase plane heat pipes diverges at an angle of between0 and 90 degrees.
 12. The cooling system of claim 3, wherein a centralone of the plurality of phase plane heat pipes is non-divergent.
 13. Thecooling system of claim 3, wherein an outer one of the plurality ofphase plane heat pipes diverges from a central one of the plurality ofphase plane heat pipes.